1. Field of the Invention
This invention relates to an article of footwear, and more particularly to an athletic shoe having a self-pumping chamber for producing a continuous supply of fluid. The fluid produced by the chamber may be used to provide ventilation to the foot of the wearer or to improve the fit or cushioning aspects of the shoe.
2. Related Art
Articles of footwear, including athletic shoes, typically include a flexible upper and a sole. Such articles of footwear are sold in a variety of sizes according to the length and width of the wearer's foot. However, even feet of similar length and width do not necessarily have the same configuration. Therefore, the upper may be adjustable to accommodate various configurations of the human foot. Such adjustment may include medial and lateral side portions which, when tensioned, provide support to the foot. In addition, particularly in the case of athletic footwear, the upper may include an ankle portion which encompasses a portion of the ankle region of the foot and thereby provides support thereto.
The support provided by the upper may be enhanced by the provision of an adjustable fastening system on the upper, which allows the wearer to adjust the tension of the upper on the foot. One common example of a fastening system includes an eyestay opening which overlies the instep portion of the foot. A tongue piece may be provided on the upper beneath the eyestay opening. An eyestay piece is attached to the upper at the eyestay opening. The eyestay piece may include eyelets or other type apertures which allow, for example, a shoe lace, or a strap, to be fed therethrough. By altering the tension on the shoe lace or strap, the distance between the opposing edges of the eyestay opening is varied. Hence, the fit of the shoe in general, can be altered by adjusting the fastening system.
While such fastening systems are common, they do suffer from several disadvantages, for example, when the shoe lace or strap is drawn too tightly, the fastening system puts pressure on the instep of the foot. Such localized pressure is uncomfortable to the wearer and can make it difficult for the shoe to be worn for prolonged periods of time. Furthermore, while such fastening systems allow the upper of the shoe to be adjustable to accommodate varying foot and ankle configurations, they do not necessarily mold to the contour of individual feet and thereby provide additional support for the foot. Moreover, no matter how much tension is exerted on the medial and lateral side portion, there still remain areas of the foot which are not supported by the upper, due to the irregular contour of the foot.
Heretofore, various devices have been proposed for adjusting the fastening force of an upper on the foot. Many provide an inflatable bladder within the interior of the footwear. One example is U.S. Pat. No. 4,583,305 to Miyamoto which provides an inflatable air pack within the interior of a ski boot. The air pack overlies the instep of the foot and is inflated by an electronic pump affixed to the rear ankle portion of the boot. The wearer may select a desired air pressure for the interior of the air pack. The electronic pump has a sensor which causes a pump motor to stop sending air to the pack when the pressure within the air pack has reached the desired pressure. The air pack may be deflated by a electronic switch.
The Miyamoto device suffers from disadvantages which are overcome by the present invention. For example, the device does not provide for diffusion of air from within the pack. Therefore, when the air pressure within the air pack decreases due to diffusion, the Miyamoto device provides no means for sensing diffusion and for automatically transferring air to the pack to return it to the preselected pressure. As a result, the air pressure within the pack does not maintain constant.
Similarly, inflatable devices have been proposed to provide firm support and restraining forces against the foot, while conforming to the irregular contour of the foot. One example is U.S. Pat. No. 3,685,176 to Rudy. This patent discloses a gas-inflatable bladder also disposed within a ski boot, which when inflated, exerts force on the instep, achilles heel and ankle of the foot to maintain the same in proper position within the boot.
The Rudy bladder has disadvantages of its own which are overcome by the present invention. First, the Rudy bladder includes no means for adjusting the fluid pressure once the bladder has been inflated. Second, the Rudy bladder is inflated using a pressurized gas which is more costly than simply using ambient air. Furthermore, the Rudy bladder does not provide for diffusion, i.e. no means is provided for automatically re-inflating the bladder upon such diffusion.
Therefore, the need exists for an article of footwear which provides firm, comfortable support to the foot while also conforming to the foot's irregular contour. Furthermore, the need exists for an article of footwear which provides an inflatable bladder which allows the fluid pressure within to be preselected and which maintains that preselected pressure by continually transferring air from the atmosphere thereto.
Still other articles of footwear having an inflatable bladder to improve the fit of the upper utilize a pumping mechanism which is activated by movement of the upper portion of the wearer's foot. One such article of footwear is disclosed in U.S. Pat. No. 4,178,013 to Bataille. Although the pumping mechanism of the Bataille patent is capable of supplying fluid to an inflatable bladder, the device of the Bataille patent suffers from a major disadvantage. As the inflatable bladder of the Bataille patent reaches a highly pressurized state, the upper portion of the wearer's foot is incapable of movement necessary to activate the pumping mechanism. Thus, the supply of air to the bladder is interrupted as the pressure within the bladder increases.
In an effort to move away from pumping mechanisms dependent upon movement of the upper portion of the wearer's foot, pumping chambers disposed within the sole of the shoe have been developed. An example of such a shoe is disclosed in International Publication No. WO 87/03789 to Johnson. The Johnson publication discloses an athletic shoe having a pumping cavity in the sole of the shoe. The pumping cavity of the Johnson publication includes at least one inlet for drawing air into the pumping cavity and at least one outlet for expelling air from the pumping cavity. The shoe of the Johnson publication suffers, however, from the fact that the inlet and outlet of the pumping cavity are exposed to the atmosphere exterior of the shoe. Thus, as the wearer moves, dirt and other particulate matter is capable of entering the inlet and outlet of the pumping cavity to interfere with operation of the same. In addition to the foregoing disadvantage, the shoe of the Johnson publication does not include a pumping cavity in the forefoot portion of the shoe. Thus, if the wearer fails to land on or strike the heel of the shoe, no pumping action is produced.
Yet another device having a pumping mechanism in the sole of the shoe is disclosed in U.S. Pat. No. 4,763,426 to Polus et al. The Polus patent discloses a shoe having a midsole and an outsole. A chamber body is disposed within the interior of the midsole to provide cushioning to the foot of the wearer. Although the chamber body of the Polus patent is capable of providing air to a cushioning device of the sole, the Polus device includes many component parts which must be separately assembled into the shoe and are expensive to manufacture.
Thus, there is a need for an athletic shoe having a pumping mechanism which continuously produces a supply of fluid, such as air, for inflating an inflatable support system, for pressurizing a pneumatic cushioning device, or for any other purpose requiring a continuous supply of fluid. There is another need for a pumping mechanism having an inlet and an outlet which is not open to the atmosphere. There is yet another need for an athletic shoe having a pumping mechanism in the forefoot and heel regions of the shoe. There is still another need for a pumping mechanism which is inexpensive to manufacture and includes few component parts. Finally, it is desirable to provide a self-pumping mechanism in a shoe that is completely independent of the user for producing a continuous supply of fluid such as air.